Characterization of the Single Molecular Junction

Abstract

The single molecular junction is becoming an increasingly attractive research target owing to the structural tunability, flexibility, low cost, and compatibility with electronics. From a scientific point of view, the single molecular junction gives us platform to access and investigate physical phenomena appearing at the low-dimensional nano-junction on a single molecular scale. In this chapter, we focus on the recent research progress in the characterization of the single molecular junction. One of the main issues in the single molecular junction studies is structural uncertainty in the junction. This is because there is no straightforward way to visualize and identify ultrasmall structure of a molecule trapped in nanogap electrodes. To overcome this issue and to reliably measure physical properties of the single molecular junction, researchers have developed a variety of characterization techniques. We start by introducing structure-related characterizations and analyses of plateau length, point-contact spectroscopy, inelastic electron tunneling spectroscopy, action spectroscopy, and surface-enhanced Raman spectroscopy. Then, electronic characterizations and analyses of current–voltage characteristics, thermopower measurement, and shot noise measurement are presented. Finally, we touch on force measurement, whose development is still in progress, but it provides understanding of the structure–conductance relationship in a single molecular junction.